Reticle Transfer System and Method

ABSTRACT

A fabrication system comprises a global system comprising a plurality of stockers and a global transportation system connected to the stockers, a local system coupled to the global system through the global transportation system, wherein the local system comprises a first buffer located at a boundary between the global system and the local system, a plurality of lithography apparatuses coupled to the first buffer through a local transportation system and an empty pod buffer.

BACKGROUND

The semiconductor industry has experienced rapid growth due toimprovements in the integration density of a variety of electroniccomponents (e.g., transistors, diodes, resistors, capacitors, etc.). Forthe most part, this improvement in integration density has come fromshrinking the semiconductor process node (e.g., shrink the process nodetowards the sub-20 nm node). As semiconductor devices are scaled down,new techniques are needed to maintain the electronic components'performance from one generation to the next. Device complexity isincreasing as manufacturers design smaller feature sizes and morefunctionality into integrated circuits. Such complex devices may resultin more lithography steps.

As semiconductor technologies evolve, advanced lithography techniqueshave been widely used in today's integrated circuit fabricationprocesses. Photolithographic techniques involves forming a photoresistlayer over a substrate, exposing portions of the photoresist material toa pattern of light in accordance with a desired pattern, developing thephotoresist material to remove portions of the photoresist material toexpose portions of the underlying material. A suitable etching processsuch as dry etching, wet etching and/or the like may then be performedon the substrate. As a result, the exposed underlying material may beremoved in accordance with the desired pattern.

The exposure step of the lithography process may involve a variety ofreticles (a.k.a. photo masks). Each reticle is a quartz plate havingtransparent and opaque regions. The transparent and opaque regionsreplicate a pattern representing an integrated circuit component on thesurface of a wafer. The lithography process of the integrated circuitmay comprise multiple photolithography process steps due to thecomplexity of the manufacturing process. Each lithography step mayemploy a reticle through which the pattern of a component of anintegrated circuit is generated.

An integrated circuit fab may comprise a variety of lithographyapparatuses such as steppers, immersion scanners and the like. Inaddition, the fab may have a plurality of stockers for storing wafersand reticles. The factory is automated by using automatic guidedvehicles to transport wafers and reticles and using robots to loadwafers and reticles into lithography apparatuses.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a layout of an integrated circuit fab in accordancewith an embodiment;

FIG. 2 illustrates a simplified layout of the local system of anintegrated circuit fab in accordance with an embodiment;

FIG. 3A illustrates a layout of the local system prior to moving theinternal buffer in accordance with an embodiment;

FIG. 3B illustrates a layout of the local system after moving theinternal buffer in accordance with an embodiment; and

FIG. 4 illustrates a layout of the local system in accordance withanother embodiment.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the variousembodiments and are not necessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently embodiments are discussed indetail below. It should be appreciated, however, that the presentdisclosure provides many applicable inventive concepts that can beembodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative of specific ways to makeand use the disclosure, and do not limit the scope of the disclosure.

The present disclosure will be described with respect to embodiments ina specific context, namely a reticle transportation system. Theembodiments of the disclosure may also be applied, however, to a varietyof transportation systems of an integrated circuit fab. For example, themethod described below may be applicable to a wafer transportationsystem in the fab. More particularly, the method may be applied to awafer transfer management system including moving a front openingunified pod (FOUP) from a location to another location in the fab.Hereinafter, various embodiments will be explained in detail withreference to the accompanying drawings.

FIG. 1 illustrates a layout of an integrated circuit fab in accordancewith an embodiment. For simplicity, only relevant portions of anintegrated circuit fab are included in the layout 100. One personskilled in the art will recognize that FIG. 1 is a simplified diagramillustrating the operation of transporting wafers and reticles betweendifferent locations according to an embodiment. This diagram is merelyan example, which should not unduly limit the scope of the claims. Oneof ordinary skill in the art would recognize many variations,alternatives, and modifications.

In accordance with an embodiment, an integrated circuit fab may comprisea main aisle and a plurality of bays connected to the main aisle. Aplurality of stockers may be placed at either side of the main aisle. Anoverhead transportation system over the main aisle may transportreticles and wafers from one stocker to another stocker. Alternatively,a rail system at ground level may be used to fulfill the sametransportation function.

Each bay may comprise a variety of lithography apparatuses, which areemployed to fulfill different functions of a lithography process. Thetransportation through the main aisle is commonly referred to asinter-bay transportation. On the other hand, the transportation within asingle bay is commonly referred to as intra-bay transportation.

According to different transportation characteristics, the layout 100may be divided into two regions, namely a global system 110 and a localsystem 120. As shown in FIG. 1, the global system 110 and the localsystem 120 are demarcated by a dashed line 102. In accordance with anembodiment, the global system 110 may comprise a main aisle, a railtransportation system (a.k.a. a global transportation system) and aplurality of stockers used for storing wafers and reticles. The stockersmay be a clean environment closet full of inert gas. A reticle and/orwafer may be stored in the stocker when the reticle and/or wafer are notprocessed. On the other hand, the reticle and/or the wafer may beretrieved from the stocker if the reticle and/or wafer will be used by alithography apparatus.

As shown in FIG. 1, the stockers of the global system 110 are coupled toeach other through the global transportation system. The globaltransportation system may include a variety of overhead rails andcarriers (a.k.a. automatic guided vehicles). A wafer or a reticle may beloaded into a carrier from a stocker by a robot. Furthermore, the waferor the reticle may be transported to another stocker in the globalsystem 110 or an input terminal of the local system 120.

It should be noted that the container carrying reticles may be differentfrom the container carrying wafers. In accordance with an embodiment,the reticle container may be a reticle storage pod (RSP). On the otherhand, the wafer container may be a front opening unified pod (FOUP).

The local system 120 is coupled to the global system 110 through atleast one overhead rail. There may be a buffer located at the boundarybetween the local system 120 and the global system 110. A wafer or areticle may be temporarily stored at the buffer when the overhead railcoupled to the buffer is jammed or the destination apparatus of thelocal system 120 is not available.

The local system 120 may comprise a variety of lithography apparatusessuch as immersion scanners, stepper and/or the like. All lithographyapparatuses are coupled to each other through a local transportationsystem. The local transportation system may include a variety ofoverhead rails and carriers. A wafer, a reticle, a group of waferscarried by a pod such as FOUP may be loaded into/from a scannerfrom/into a carrier by a robot such as a 3-axis reticle handling arm.Furthermore, the wafer or the reticle may be transported to anotherscanner or to the global system through the overhead rail of the localtransportation system. The detailed layout of the local system 120 willbe described below with respect to FIG. 2.

One advantageous feature of dividing a fab layout into a global systemand a local system is that the local system may be of an independenttransportation system. As such, the system shown in FIG. 1 can avoidsome common issues of the close-loop transportation system of a fab. Forexample, in order to short the response time, the close-looptransportation may employ many carriers cycling in loop to keep a shortresponse time and need a dedicated loop for each scanner. Furthermore,the system may need a variety of rails between stockers and scanners tosolve the traffic jam issue. By employing the layout shown in FIG. 1,the traffic between the global system and the local system has beenreduced. As such, the traffic jam between the global system and thelocal system may be alleviated. Therefore, few carriers are needed sothat the production cycle time and tool efficiency may be improved.

FIG. 2 illustrates a simplified layout of the local system of anintegrated circuit fab in accordance with an embodiment. The localsystem 120 may comprise a plurality of lithography apparatuses such asscanners. The scanners reside along two sides of a local aisle. As shownin FIG. 2, scanners A1, A2, A3, A4, A5, A6 and A7 reside at a first sideof the local aisle. Scanners B1, B2, B3, B4, B5, B6 and B7 reside at asecond side of the local aisle. There may be a transportation systemlocated over the local aisle. The transportation system may include tworails, namely a first rail 222 and a second rail 224. As shown in FIG.2, the first rail 222 provides reticle/wafer transportation for thescanners A1, A2, A3, A4, A5, A6 and A7. Likewise, the second rail 224provides reticle/wafer transportation for the scanners B1, B2, B3, B4,B5, B6 and B7.

It should be noted that depending on different applications andconstraints, the rails may be built at ground level. Alternatively, anoverhead rail system may be employed to save ground level space. Itshould further be noted while the system and method described below maybe applicable to both reticles and wafers, a reticle transfer system isused as an example to illustrate the innovative aspects of variousembodiments.

Each scanner such as A1 may include a scanner apparatus 252 and areticle port 254 embedded in the scanner apparatus 252. In particular,the reticle port 254 may be a loading platform located in the scannerand adjacent to a process chamber of the scanner apparatus 252. Aconveyor 258 couples the scanner apparatus 252 with the localtransportation system. More particularly, as shown in FIG. 2, when areticle is transported from the local transportation system to thescanner apparatus 252 through the conveyor 258, a robot 256 loads thereticle into the reticle port 254. On the other hand, when a reticle isnot processed, the reticle is loaded into the reticle port 254 from thescanner apparatus 252. The robot 256 further loads the reticle into theconveyor 258 from the reticle port 254. In accordance with anembodiment, the robot 256 may be a 3-axis reticle handling arm. Itshould be noted that scanners can be employed to store reticles. In someembodiments, a scanner can accommodate 6 to 8 reticles.

There may be two reticle buffers 212 and 214 in the local system 120.The reticle buffers 212 and 214 are coupled to both the first rail 222and the second rail 224. As shown in FIG. 2, the first reticle buffer212 and the second reticle buffer 214 are on opposite sides of the localaisle. One of the reticle buffers (e.g., reticle buffer 212) mayfunction as a buffer between the global system 110 and the local system120.

In addition, the reticle buffers 212 and 214 may be used to store emptypods including FOUP, RSP and/or the like. More particularly, a pod suchas RSP is a closed container carrying about one reticle. When a reticleis loaded into its corresponding scanner apparatus, the empty pod may betransported to a stocker according to a conventional factory automationmechanism. Such a long distance transfer may cause a traffic jam, whichin turn delays the response time of loading/unloading reticles. Storingempty pods in the reticle buffers 212 and 214 may reduce long distancetransportation. As a result, the traffic jam issue of the system can bealleviated.

It should be noted that storing empty pods in the reticle buffers 212and 214 is merely an example, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. For example, in a fabhaving an overhead rail transportation system in the local system, theempty pods may be stored at an overhead storage area adjacent to theoverhead rail.

In consideration with the location of lithography apparatuses, the localsystem 120 may be divided into two service areas. The first service area202 extends from the first reticle buffer 212 to the conveyor of thescanner A5. The second service area 204 extends from the conveyor of thescanner A5 to the second reticle buffer 214. There may be two carriers(a.k.a vehicles) 216 and 217 dedicated to the first service area 202.Likewise, carriers 218 and 219 are employed to transport reticle withinthe second service area 204. It should be noted the definition of thefirst service area and the second service area is not fixed. Theterritory of each service area may change by adjusting an internalbuffer. The detailed operation of the internal buffer will be describedbelow.

It should be recognized that while FIG. 1 illustrates the local system120 with fourteen scanners and two service areas, the local system 120could accommodate any number of scanners and service areas. The numberof scanners and service areas illustrated herein is limited solely forthe purpose of clearly illustrating the inventive aspects of the variousembodiments. The present disclosure is not limited to any specificnumber of scanners and service areas.

The local system 120 may further comprise an internal buffer 206 locatedbetween the first reticle buffer 212 and the second reticle buffer 214.More particularly, the internal buffer 206 is a movable component. Thedefault position of the internal buffer 206 is at the boundary of thefirst service area 202 and the second service area 204. In considerationwith the need of transporting reticles efficiently, the location of theinternal buffer 206 may change accordingly. The detailed operation ofthe internal buffer 206 will be described below with respect to FIG. 3and FIG. 4.

One advantageous feature of having the local system layout shown in FIG.2 is that the adjustable internal buffer helps to improve the scannerproductivity so that the total cost of manufacturing integrated circuitscan be reduced.

FIG. 3A illustrates a layout of the local system prior to moving theinternal buffer in accordance with an embodiment. As indicated by adashed curve 302, a reticle will be transported from the scanner A1 tothe scanner A6. A system controller (not shown) may check the activitiesof both service areas before adjusting the location of the internalbuffer 206. In accordance with an embodiment, the second service area isidle. In other words, there is no reticle transportation in the secondservice area. The system controller may move the internal buffer 206from its default point scanner A5's conveyer to a location beyond thescanner A6 so that the carrier 216 may deliver the reticle to thescanner A5 directly.

FIG. 3B illustrates a layout of the local system after moving theinternal buffer in accordance with an embodiment. The internal buffer206 has been moved to the location adjacent to the conveyor of thescanner A7. As a result, the carrier 216 may deliver the reticle to theconveyor of the scanner A6 directly. One advantageous feature of havingadjustable internal buffer is that the internal buffer stage may bebypassed so that the time of moving a reticle may be reduced.

FIG. 4 illustrates a layout of the local system in accordance withanother embodiment. As indicated by dashed curves 402 and 404, a firstreticle will be transported from the scanner A1 to the scanner A6. Atthe same time, a second reticle will be transported from the scanner A7to the scanner A6. As a result, there is conflict between these tworeticle moving events. In consideration with this conflict, the systemcontroller may not adjust the location of the internal buffer 206. Thesecond reticle will be transported to the scanner A6 by the carrier 218.The first reticle will be transported to the internal buffer 206 by thecarrier 216. After the carrier 218 is available, the first reticle isloaded into the carrier 218 and transported to the scanner A6subsequently.

Although embodiments of the present disclosure and its advantages havebeen described in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the disclosure as defined by the appendedclaims.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the present disclosure, processes, apparatuses,manufacture, compositions of matter, means, methods, or steps, presentlyexisting or later to be developed, that perform substantially the samefunction or achieve substantially the same result as the correspondingembodiments described herein may be utilized according to the presentdisclosure. Accordingly, the appended claims are intended to includewithin their scope such processes, apparatuses, manufacture,compositions of matter, means, methods, or steps.

What is claimed is:
 1. A fabrication system comprising: a global systemcomprising a plurality of stockers and a global transportation systemconnected to the stockers; a local system coupled to the global systemthrough the global transportation system, wherein the local systemcomprises: a first buffer located at a boundary between the globalsystem and the local system; a plurality of lithography apparatusescoupled to the first buffer through a local transportation system; andan empty pod buffer.
 2. The fabrication system of claim 1, wherein: theglobal transportation system includes a plurality of rail loopsconnected between the plurality of stockers and the local system.
 3. Thefabrication system of claim 1, wherein the lithography apparatus is ascanner.
 4. The fabrication system of claim 1, further comprising: aconveyor coupled between the local transportation system and thelithography apparatus; a robot configured to move a reticle between theconveyor and the lithography apparatus; and a reticle port embedded inthe lithography apparatus, wherein the robot is coupled between thereticle port and the conveyor.
 5. The fabrication system of claim 4,wherein: the robot is a 3-axis reticle handling arm.
 6. The fabricationsystem of claim 1, wherein the local transportation system comprises: anaisle, wherein a first terminal of the aisle is connected to the firstbuffer; a first rail coupled between the first buffer and a first groupof lithography apparatuses; a second rail coupled between the firstbuffer and a second group of lithography apparatuses, wherein the firstgroup of lithography apparatuses and the second group of lithographyapparatuses are on opposite sides of the aisle; a second bufferconnected to a second terminal of the aisle; and an internal bufferlocated between the first buffer and the second buffer, wherein theinternal buffer is adjustable.
 7. The fabrication system of claim 6,further comprising: a first service area located from the first bufferto the internal buffer; and a second service area located from theinternal buffer to the second buffer.
 8. The fabrication system of claim7, further comprising: a first carrier on the first rail, wherein thefirst carrier is located in the first service area; a second carrier onthe first rail, wherein the second carrier is located in the secondservice area; a third carrier on the second rail, wherein the thirdcarrier is located in the first service area; and a fourth carrier onthe second rail, wherein the fourth carrier is located in the secondservice area.
 9. The fabrication system of claim 1, wherein: the emptypod buffer is located at an overhead region.
 10. The fabrication systemof claim 1, wherein: the empty pod buffer is located at the firstbuffer.
 11. A system comprising: a plurality of stockers configured tostore reticles, wherein the stockers are located in a first regioncomprising: a first transportation system configured to move thereticles between different stockers; a plurality of lithographyapparatuses in a second region, wherein the second region is connectedto the first transportation system through a first buffer; a secondtransportation system in the second region, wherein the secondtransportation system is connected to the first buffer and the pluralityof lithography apparatuses, wherein the second transportation systemcomprises: a first service area configured to serve a first group oflithography apparatuses; a second service area configured to serve asecond group of lithography apparatuses; and an internal buffer locateda boundary between the first service area and the second service area;and an empty pod buffer.
 12. The system of claim 11, wherein: the firstsystem is a global system configured to carry long distancetransportation.
 13. The system of claim 11, wherein: the second systemis a local system comprising: an aisle, wherein a first terminal of theaisle is connected to the first buffer; a first rail coupled between thefirst buffer and a first group of lithography apparatuses; a second railcoupled between the first buffer and a second group of lithographyapparatuses, wherein the first group of lithography apparatuses and thesecond group of lithography apparatuses are on opposite sides of theaisle; and a second buffer connected to a second terminal of the aisle.14. The system of claim 11, wherein: the internal buffer is anadjustable buffer.
 15. The system of claim 11, wherein: the lithographyapparatus is a scanner.
 16. A method comprising: placing an internalbuffer at a default position of a local system, wherein the defaultposition is a first boundary between a first service area and a secondservice area; loading a reticle from a first apparatus into a firstcarrier, wherein the first apparatus and the first carrier is located inthe first service area; determining whether a conflicting reticletransfer event occurs in the second service area; and transporting thereticle to a second apparatus in the second service area.
 17. The methodof claim 16, further comprising: after the step of determining whether aconflicting reticle transfer event occurs in the second service area,adjusting a position of the internal buffer to set a second boundarybetween the first service area and the second service area; andtransporting the reticle to the second apparatus by the first carrier.18. The method of claim 16, further comprising: after the step ofdetermining whether a conflicting reticle transfer event occurs in thesecond service area, storing the reticle in the internal buffer; andtransporting the reticle to the second apparatus by a second carrierlocated in the second service area.
 19. The method of claim 16, furthercomprising: loading the reticle from a stocker of a global system;transporting the reticle to a first buffer by a global transportationsystem, wherein the first buffer is located at a boundary between theglobal system and the local system; and transporting the reticle fromthe first buffer to the first apparatus by using the first carrier. 20.The method of claim 19, further comprising: moving the reticle from thefirst carrier to a conveyor connected to the first apparatus; loadingthe reticle from the conveyor to a reticle port embedded in the firstapparatus by a 3-axis reticle handling arm; and moving the reticle fromthe reticle port to the first apparatus.